United are the front runners to reclaim for former ace - but they could benefit even if Ronaldo decides to move elsewhere.

Why? Well because of FIFA's solidarity mechanism rule - which any club a player was coached by before he turned 23 are legible to receive a percentage of his future fee.

Cristiano Ronaldo wants to leave Real Madrid this summer (Image: PA)

Sporting Lisbon could get a juicy cash bonus this summer if Cristiano Ronaldo goes on the move (Image: Reuters)

According to article 21 of FIFA's 'Regulaltions on the status and transfer of players': "If a professional is transferred before the expiry of his contract, any club that has contributed to his education and training shall receive a proportion of the compensation paid to his former club (solidarity contribution)."

In Ronaldo's case his former clubs United, Sporting Lisbon and Nacional are all to share a 5 per cent pot of the fee.

The split would work out as United taking 2.5 per cent, Sporting 2.25 per cent and National, where Ronaldo didn't make a first team appearance, taking the remaining 0.25 per cent.

Cristiano Ronaldo made nearly 300 appearances last time around at Manchester United (Image: Getty)

If a suitor splashes £100m on Ronaldo, for example, that would mean United would be handed £2.5m.

However, the fee is expected to be much higher - with a release clause of £875m and Real sticking a price tag of £174.5m on their prized posession.

Ronaldo played 292 times at Old Trafford after joining from Sporting for £12m in 2003.

He departed six seasons later for Real in a then-world record £80m deal.